Snap-action switches normally urged toward one of two operating positions



R. M. FLANAGAN SNAP-ACTION SWITCHES NORMALLY URGED TOWARD ON 3,365,556 E OF TWO Jan. 23, 1968 OPERATING POSITIONS 3 Sheets-Sheet 1 Filed March ,3, 1966' INVENTOR.

ROBERT M. FLANAGAN Jan; 23, 1968 v R, M, FLANAGAN 3,365,556 S SNAP-ACTION SWITCHES NORMALLY URGED TOWARD ONE OF TWO OPERATING POSITIONS Filed March L, 1966 5 Sheets-Sheet F3 YTZYE INVENTOR.

ROBERT M. FLANAGAN BY AT RNEYS Jan. 23, 1968 R. M. FLANAGAN 3,365,556 SNAP-ACTION SWITCHES NORMALLY URGED TOWARD ONE OF TWO OPERATING POSITIONS Filed March 2%, 1966 3 Sheets-Sheet 5 INVENTOR.

ROBERT M. FLANAGAN AT TO United States Patent SNAP-ACTEON SWITCHE NGRMALLY URGED TOWARD ONE OF TWO OPERATING POSITIONS Robert M. Flanagan, Summit, N.J., assignor to Elastic Stop Nut Corporation of America, Union, N.J., a corporation of New .lersey Filed Mar. 2, 1966, Ser. No. 531,133 Claims. (Cl. 200-67) The present invention relates generally to electric switches and pertains more specifically to improved snapaction switches of the type usually employed in combination with time delay control apparatus. Improved snapaction switches of the present invention are particularly useful for opening or closing electrical circuits after the lapse of a predetermined time interval following the actuation of the time delay control apparatus by an operator.

Snap-action electric switches utilizing a variety of overcenter mechanisms have been employed in combination with time delay control apparatus to vary rapidly open or close the contacts of the switches despite the relatively slow movement of the switch actuating means provided by the time delay control apparatus. Generally, the time delay control apparatus has a reeiprocable motion transmitting member which travels at a predetermined rate to meter the predetermined time interval between activation of the apparatus and the opening or closing of the contacts of the switch. Usually, the over-center mechanism biases a movable contact either toward or away from a fixed contact until the motion transmitting member drives the over-center mechanism through a dead-center position to reverse the bias of the mechanism and rapidly throw the movable contact in a direction opposite to that in which it was originally biased to either make or break electrical contact with the fixed contact. A problem arises, however, when the over-center mechanism approaches its dead-center position slowly since at or near that position of the over-center mechanism the bias upon the movable contact is considerable reduced, even to the point of no bias at all at the dead-center position, and instead of a rapid breaking of electrical contact, the contact pressure between the movable and fixed contacts will slowly be reduced with consequent deleterious effects such as arcing and burning of the contacts. The problem becomes particularly acute in two-pole switches where it is very desirable to assure that electrical contact at both poles will break practically simultaneously.

In certain installations, such switches must be continuoulsy biased toward one operating position, in which instances movement of the motion transmitting member must drive the over-center mechanism against the fixed bias, as well as against the reversible bias of the overcenter mechanism itself, when the switch is actuated to the other operating position. Since the fixed bias acts against the movement of the over-center mechanism, rapid reversal of the bias of the over-center mechanism is hampered in the direction of such movement and the ability of such switches to exhibit an effective snap-action in that direction is essentially defeated.

It is therefore an important object of the invention to provide improved snap-action electric switches in which at least a pair of contacts are continuously biased either into or out of engagement with one another and in which rapid opening or closing of the contacts against the continuous bias is attained in response to relatively slow movement of the switch actuating means against the continuous bias.

Another object of the invention is to provide improved snap-action switches as above wherein at least one movable contact is biased by over-center means in one direction with sufllcient force to assure good electrical contact with at least one corresponding fixed contact until the bias of the over-center means is rapidly reversed in response to relatively slow movement of the switch actuating means against the continuous bias to enable the over-center means to bias the movable contact in another direction.

Still another object of the invention is to provide improved snap-action switches as above having at least two poles wherein at least two movable contacts are biased in one direction with suflicient force to assure good electrical contact with at least two corresponding fixed contacts until the bias is rapidly reversed in response to relatively slow movement of the switch actuating means to bias the movable contacts in another direction and effect essentially simultaneous rapid breaking of contact at all poles of the switch.

A further object of the invention is to provide improved snap-action switches for use in combination with time delay control apparatus wherein the switch is constantly biased toward one position of operation and a reciprocable motion transmitting member moves relatively slowly against the constant bias to actuate the switch in response to such slow movement.

A still further object of the invention is to provide improved snap-action switches as described above which may be actuated with less force than corresponding snapaction switches of the prior art.

Another object of the invention is to provide a snapaction switch of the type described above wherein the sensitivity of the switch to movement of the switch actuating means may be varied.

Still another object of the invention is to provide improved snap-action switches of the type described which are relatively simple in operation and construction, easy to manufacture, and efiicient and dependable in use.

These and other objects are attained in the present invention which may be described briefly as a snap-action electric switch capable of being operated between two positions and normally urged toward one of the two positions, the switch comprising a base, at least one first contact fixed to the base, a lever member mounted on the base for movement in either of two directions between first and second positions, a contact arm movable in either of the two directions between two positions in response to the movement of the lever member between the first and second positions, at least one second contact carried by the contact arm for engagement with the corresponding first contact when the contact arm is in one of the two positions and disengagement from the corresponding first contact when the contact arm is in the other of the two positions, spring means biasing the lever member toward one of its first and second positions, over-center spring means for biasing the contact arm in either of the two directions from a dead-center position of the over-center spring means located between the first and second positions of the lever member, a link coupling the overcenter spring means with the lever member such that movement of the lever member from one of its first and second positions toward the other of those positions will move the over-center spring means through its dead-center position and reverse the bias of the over-center spring means so as to urge the contact arm toward the other of the first and second positions of the contact arm, and motion transmitting means movable in either of the two directions and engaging the lever member during movement in one of the directions to move the lever member relatively slowly against the bias of the spring means, the link cooperatively engaging the lever member for pivotal movement relative thereto such that as the lever member is moved slowly by the motion transmitting means against the bias of the spring means and the over-center spring means passes slowly through the dead-center position, the link will pivot rapidly with respect to the lever member to allow relatively rapid reversal of the bias of the overcenter spring means and rapid transfer of the contact arm from one to the other of the contact arm positions. A further over-center spring means may couple the base and the contact arm for biasing the contact arm in either one of the two directions from a dead-center position of the further over-center spring means and biasing the contact arm in the same direction as the bias of the earlier defined first over-center spring means when the contact arm is in either one of its two positions to maintain the contact arm in that one position while the lever member is moved from one oward the other of the first and second positions and until the first over-center spring means is moved through its dead-center position by movement of the lever member whereupon the bias of the first over-center spring means is reversed and directed against the bias of the further over-center spring means, the relative magnitudes of the bias forces of the first and further ovencenter spring means being such that the bias force of the further over-center spring means is overcome by the bias force of the first over-center spring means, when the forces are directed against one another, to urge the contact arm toward the other of the two positions and the further overcenter spring means through its dead-center position whereupon the bias of the further over-center spring means is reversed so that both the first and further overcenter spring means will bias the contact arm toward the other of the two positions. The switch may include stop means on the base disposed relative to the lever member for precluding movement of the lever member beyond the first and second positions, the stop means being selectively adjustable to enable accurate location of each of the first and second positions and vary the sensitivity of the switch.

The novel features of the invention, as well as the invention itself. both as to its organization and method of operation, will be more fully understood from the following detailed description of an embodiment of the invention illustrated in the accompanying drawing in which similar reference characters refer to similar parts throughout, and in which:

FIGURE 1 is an elevational view of time delay control apparatus employing a snap-action switch constructed in accordance with the invention, portions of the apparatus being removed to show inner details;

FIGURE 2 is an enlarged cross-sectional view taken along line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged cross-sectional view taken along line 3-3 of FIGURE 2 and illustrating component parts of the switch;

FIGURE 4 is an enlarged cross-sectional view taken along line 44 of FIGURE 2;

FIGURE 5 is an enlarged cross-sectional view taken along line 5-5 of FIGURE 2;

FIGURE 6 is a cross-sectional view similar to FIG- URE 3, but with the component parts in another operating position;

FIGURE 7 is a cross-sectional view similar to FIG- URE 4, but with the component parts in another operating position;

FIGURE 8 is an enlarged detail of component parts of the switch viewed as in FIGURE 2; and

FIGURES 9 through 12 are diagrammatic drawings illustrating the operation of the switch.

Referring to the drawing, and particularly to FIGURE 1, a time delay control apparatus is designated generally at It) and includes a timing head 12 cooperatively engaging a motion transmitting member illustrated in the form of a rod 14 arranged for reciprocatory motion. The rod 14 is moved in either of two opposite directions indicated by the double'headed arrow 16, the rate of movement in both directions being controlled by the head 12. The timing head 12 may operate in any one of a variety of Ways now well known in the art. Since the particular details of the timing head 12 of the time delay control apparatus do not form a part of the present invention,

they will not be described more fully herein. It is sufficient to point out that time delay control apparatus 10 is electrically operated and includes a snap-action electric switch 29 arranged to be actuated by movement of rod 14, the apparatus being designed for electrical circuit applications where it is desirable to have, in addition to an initial time interval between energization of the apparatus 10 and actuation of switch 20, a proportionately shorter timed interval following power interruptions of relatively short duration. Thus, upon energization of apparatus It), rod 14 will move upwardly at a rate determined by timing head 12 until switch 20 is actuated to transfer the contacts of the switch from the normal position. Should apparatus 10 be deenergized as a result of a power failure at any time after switch transfer, rod 14 is arranged to drop downwardly almost instantaneously for a relatively short distance suflicient to allow switch trans fer back to the original normal position. With the switch transferred, rod 14 may continue travel downwardly at a relatively slow rate, also metered by the timing head 12, for the duration of the power failure, Upon rcenergization of the apparatus at the termination of the power failure, rod 14 will again begin traveling upwardly at a slow rate, by virtue of timing head 12, so that switch transfer will not occur until rod 14 has had an opportunity to travel upwardly over the distance traveled downwardly during the power failure, and the time delay after reenergization and before switch transfer will be equal to the deenergized time. Thus, recycling to again transfer the switch from the normal position occurs slowly and in proportion to the off time.

The most common application for apparatus 10 has been in protective circuits for vacuum tube transmitter units which require a predetermined warmup period at reduced voltage before application of full power. If a power failure occurs while the equipment is in normal operation, the vacuum tubes must be protected from reapplication of full power without sufiicient re-warming time, or alternatively, from excessively long off time following momentary outages. Apparatus 19, in effect, monitors the duration of the outage, and upon restoration of power provides another delay period approximately equal to that of the outage.

The construction and operation of snap-action switch 20 is best illustrated by turning first to FIGURES 2 through 8. Switch 20 includes a base 22 of dielectric material upon which the timing device is mounted and is provided with a pair of upper electrical contacts 24 and a pair of lower electrical contacts 26, each fixed to the base 22 by resilient contact members 28 and 3E), respectively, which are secured and electrically connected to terminals of the switch by screws 32 and 34, respectively, one such terminal being illustrated at 36 in FIGURES 4 and 7. Another pair of electrical contacts 38 is carried by a common contact arm 40 which is mounted for movement in either of two opposite upward and downward directions, along with contacts 38, between the fixed contacts 24 and 26 by resilient contact members 42 which are secured to the base by screws 44 and electrically connected to further terminals of the switch through strips 46 by means of screws 48. Thus, upward or downward movement of contact arm 40 will engage movable contacts 38 with either the upper contacts 24 or the lower contacts 26. Switch 20, then, is a two-pole switch, the two poles being represented by contacts 38 which are spaced apart transversely and located at the lateral extremities 49 (FIGURE 2) of the contact arm 40 which is fabricated of a dielectric material so that the two contacts 38 are electrically insulated from one another. Fixed contacts 24 are likewise electrically insulated from one another, as are fixed contacts 26.

In order to actuate the contact arm 40, a lever member 59 is mounted at the frst end 52 thereof to the base 22 by means of a block 54 of dielectric material which is fixed to the base by screws 56 and has a notch 58 therein for receiving end 52 which is provided with a knife-edge so that lever member 50 is mounted for ready pivotal movement about its end 52. The other end 59 of the lever member 50 is coupled to the contact arm 40 by means of a link 60 which is mounted for pivotal movement with respect to the lever member by virtue of end 59 of the lever member being received between upper hinge elements in the form of tabs 62 raised above the level of the link and lever member to overlap the lever member, the tabs extending to edges 64 thereof, and lower hinge element 66 (see FIGURE 8) of the link, all adjacent one end thereof, and the other end 68 of the link being engaged with an over-center mechanism shown in the form of first over-center spring means 70 which, in turn, engages the contact arm 40 as will be explained below.

Over-center spring means 79 includes a plunger 72 with an enlarged head 74, the plunger being received within a hollow cylinder 76 and a helical spring 78 contained within the cylinder and extending around the plunger. The cylinder has a notch 80 for receiving the other end 63 of the link, which end is provided with a knifeedge so as to be pivotally mounted in the notch, and the head 74 has a notch 82 for receiving a first end 84 of the contact arm 40, end'84 also being provided with a knife-edge so that the over-center spring means '70 may pivot with respect to the contact arm, When lever member 50 is a ta first position, as shown in FIGURE 3, helical spring 78 is in compression thereby urging head 74 away from cylinder 76 and the over-center spring means, being coupled to the lever member Sll by link 60, biases the lever member 50 toward its first position and the contact arm 40 toward its upper position where movable contacts 38 engage upper fixed contacts 24, as seen in FIG- URE 4. It is noted that in the first position of lever member 50, the lower hinge element 66 of the link 66} is urged upwardly into abutment with the lower surface of the lever member and serves as a stop for precluding further pivotal movement of link 60 in a clockwise direction relative to lever member and the link and lever member will remain in such fixed relationship as long as the other end as of the link is urged downwardly by the over-center spring means 70.

The second end 8-6 of the contact arm ltl is provided with a notch 88. A second over-center spring means 90 is shown in the form of a U-shaped leaf spring having a first end 92 with a knife-edge pivotally engaged in notch 88 of the contact arm and a second end 94 with a knifeedge pivotally engaged within a notch 96 in a block 98 of dielectric material fixed to the base 22. The second over-center spring means 90 is also in compression and provides a force biasing the contact arm 41 upwardly, in the same direction as the bias of the first over-center spring means 70 when the lever member is in the first position, as seen in FIGURE 3.

Lever member 59 is normally urged downwardly toward its first position by a spring means shown in the form of leaf spring 100 which exerts a downward bias force upon the lever member, the leaf spring 100 being illustrated in greater detail in FIGURE 5. In this normal position, the movable contacts 38 are in engagement with the upper fixed contacts 24. Lever member 50 has a slot 162 therein through which rod 14 passes. A collar 104 is fixed for movement with rod 14 below the lever member 50 and engages the lever member upon upward movement of the rod 14 to urge the lever member upwardly toward its second position, as seen in FIGURE 6, and rapidly throw the movable contacts 38 out of contact with the upper fixed contacts 24 and into contact with the lower fixed contacts 26, as seen in FIGURE 7, in a manner which will be explained in detail below. Stop means are provided in the form of a first set screw 106 threaded through the base 22 and establishing an abutment for precluding pivotal movement of the lever member downwardly beyond the first position. Since the set screw is selectively movable upwardly or downwardly,

the first position may be adjusted for accuracy and its location may be varied to vary the sensitivity of the switch as will be described below. Likewise, stop means are provided in the form of a second set screw 108 which is threaded through cantilever 109 fixed to base 22, the set screw establishing an abutment for the spring 100 for precluding upward movement of the spring and pivotal movement of the lever member upwardly beyond the second position and being adjustable in the same manner as the first set screw for corresponding purposes.

Turning now to FIGURES 9 through 12, the operation of switch 20 is illustrated diagrammatically with the reference characters corresponding to the actual structural elements described above. Referring first to FIGURE 9, switch 20 is shown in the normal position corresponding with that of FIGURES 3 and 4, with lever member 50 biased downwardly into its first position against stop means ran by spring 100 and contact arm 4i) is biased upwardly by first over-center spring means 70 to engage movable contact 38 with upper fixed contact 24. Movable contact 38 is also biased upwardly by second over-center spring means 90. Lever member 50 is also biased downwardly by the first over-center spring means 70. Upon energization of the time delay apparatus 16, rod 14 (FIG- URE 3) travels upwardly at a predetermined rate and collar 104 will engage lever member 50 and urge the lever member upwardly with a force indicated by arrow 110. The force is great enough to overcome the bias of spring 100 and over-center spring means 70 so that the lever member 50 is pivoted about its end 52 and first over-center spring means 70 is compressed and pivoted about its ends until the over-center spring means 70 reaches a dead-center position illustrated in FIGURE 10. Up to this point, the lever member 5d and the link 60 have moved in unison by virtue of the downward bias of over-center spring means 70 upon the link 6% as explained above. At the dead-center position of the first over-center spring means 70, the upward bias upon contact arm 40 provided by the over-center spring means 70 is considerably reduced since the force of means 7i! is directed largely horizontally along contact arm 40. In ordinary snap-action switches, the over-center spring means would be moved relatively rapidly through the dead-center position and the movable contact would be driven rapidly downwardly by reversal of the bias provided by the overcenter spring means to quickly break contact with the fixed contact. However, where the lever member, and consequently the over-center spring means, is moved relatively slowly, as by the slow movement of the motion transmitting member of time delay control apparatus It the dead-center position is approached slowly and the decreased bias upon the movable contact will result in decreased pressure between the movable contact and the fixed contact which results in an unstable condition at the point of electrical contact, leading to deleterious effects such as arcing with consequent burning and erosion of the contact material. In a two-pole switch, the unstable condition may result in undesirable breaking of electrical contact at one pole before con-tact is broken at the other pole. In order to overcome such difii culties, switch 20 is provided with the second over-center spring means which maintains an upward bias upon contact arm 40 and retains adequate contact pressure between movable contact 38 and fixed upper contact 24 while the first over-center spring means 70 is moved through the dead-center position, even though the movement is relatively slow. Once the first over-center spring means 70 is moved beyond the dead-center position, as seen in Fl"- -URE 11, the bias of the first over-center spring means is reversed with respect to the contact arm 40 and tends to urge the contact arm 40 downwardly to transfer the movable contact. However, before the contact arm can be moved downwardly, the downward bias force of means 70 should become great enough to rapidly accelerate the contact arm from the upper rest position shown in FIG- URES 9 and and must become great enough to overcome the upward bias of the second over-center spring means 90. The pivotal movement of the first means 70 from the essentially horizontal attitude at the dead-center position shown in FIGURE 10 to an attitude where there is a substantial vertical bias directed downwardly, as seen in FZGURES l1 and 12, cannot occur rapidly enough through continued pivotal movement of lever member 50 since such continued pivotal movement can only proceed at the rate of movement of rod 14, the presence of spring 136 precluding more rapid pivotal movement. However, the relatively small upwardly directed vertical bias force available immediately after the first over-center spring means '70 passes through the deadcenter position is sufiicient to pivot link as relative to lever member 50, as seen in FIGURE 11, practically instantaneously to very quickly eifect sufiicient pivoting of over-center means 70 to arrive at an attitude which will provide the necessary bias force to effect rapid downward movement of the contact arm to break the electrical contact between movable contact 38 and upper fixed contact 24, the downward bias force thus attained in first over-center spring means 70 becoming great enough to drive contact arm 40 through the dead-center position of the second over-center spring means 90 as pictured in FIGURE 11. Upon passage of the second over-center spring means 90 through its dead-center position, the bias of means 90 will be reversed with respect to the contact arm 40 and the contact arm will be biased downwardly by second means 90 as well as by the first means 76 to urge movable contact 38 into electrical contact with fixed lower contact 26, as shown in FIGURE 12. Pivotal movement of the link 60 relative to the lever member 50 is limited by virtue of the edges 64 of the tabs 62 (see FIGURES 6 and 8) engaging the upper surface of the lever member to preclude further relative movement. Counterclockwise pivotal movement of lever member 53 in response to upward movement of rod 14 can continue until the lever member and spring 100 arrive at the second position against stop means 108 and the switch 20 is in a configuration corresponding to that of FIGURES 6 and 7. Should there be a power failure such that the time delay control apparatus 10 becomes deenergized, rod 14 will drop practically instantaneously to displace collar 104 downwardly a distance sufficient to allow spring 100 to return the switch 20 to the normal position shown in FIGURES 3 and 4 and illustrated diagrammatically in FIGURE 9, the downward displacement of collar 104 being illustrated in phantom at 114 in FIG- URE 3. After such an instantaneous initial drop from the position shown in FIGURE 6 to that shown in phantom at 114 in FIGURE 3, collar 104 and rod 14 may continue downward movement at a relatively slow rate determined by timing head 12 for the duration of the outage. Upon restoration of power and reenergization of apparatus 10, rod 14 will reverse its direction of travel so that collar 104 can once again engage lever member 50 and actuate the switch 20. Such actuation will occur at a time interval after restoration of power, the duration of which interval is proportional to the duration of the outage. During the return of switch 20 to its normal configuration (FIGURE 3) by the action of leaf spring 100 against the lever member 50, the bias of both the first and second over-center spring means 70 and 90 are reversed and the link 60 is pivoted with respect to the lever member back to its normal position in alignment with the lever member with lower hinge element 66 engaging the lower surface of the lever member. The bias force provided by leaf spring 100 is great enough to actuate the switch against the bias force of the first over-center spring means '70 to transfer the movable contact 38 when collar I04 drops to the position indicated at 114 and restore the switch from the configuration illustrated diagrammatically in FIGURE 12 to that shown in FIG- URE 9.

Each of the stop means 106 and W8 is adjustable to selectively vary the location of the first and second positions of lever member 50. By varying the location of the first and second positions with respect to the corresponding dead-center position of the first over-center spring means 76, the amount of work required to drive the lever member from one of the first or second positions through. a corresponding dead-center position can be adjusted to increase or decrease the sensitivity of the switch 29', Hence, the amount of work which must be performed by the motion transmitting member in moving lever member 50 upwardly from the first position through the deadcenter position of means 76 illustrated in FIGURE 10 may be decreased by turning set screw 1% to raise the first position closer to the dead-center position and the switch 20 becomes more sensitive to smaller amounts of upward movement of the motion transmitting member. Likewise, adjustment of set screw 103 downwardly will render switch 20 more sensitive to smaller amounts of downward movement of the motion transmitting member.

From the foregoing description it will be apparent that the invention provides a snap-action switch wherein rapid making or breaking of a pair of contacts is attained despite the continuous bias of the switch toward one normal position and despite relatively slow movement of the switch actuating means in the direction which effects operation of the switch against the continuous bias. The switch is sensitive enough to movement of an actuating means to render the switch particularly well suited to employment in connection with time delay control apparatus and the sensitivity may be adjusted to achieve optimum operation.

It is to be understood that the above detailed description of an embodiment of the invention is provided by way of example only and is not intended to restrict the invention. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

l. A snap-action electric switch capable of being 0perated between two positions and normally urged toward one of said two positions, the switch comprising:

a base;

at least one first contact fixed to the base;

a lever member mounted on the base for movement in either of two directions between first and second positions;

21 contact arm;

means mounting said contact arm for movement with respect to said base in either of said two directions between two positions in response to the movement of the lever member between the first and second positions;

at least one second contact carried by the contact arm for engagement with the corresponding first contact when the contact arm is in one of said two positions and disengagement from the corresponding first contact when the contact arm is in the other of said two positions;

spring means mounted with respect to the base for biasing the lever member toward one of said first and second positions;

first over-center spring means for biasing the contact arm in either of said two directions from a deadcenter position of the over-center spring means located between the first and second positions of the lever member;

a link operatively engaging the over-center spring means and the lever member to couple the first over-center spring means with the lever member such that move ment of the lever member from one of said first and second positions toward the other of said positions will move the first over-center spring means through said dead-center position and reverse the bias of the 9 first over-center Spring means so as to urge the contact arm toward the other of said first and second positions of the contact arm; motion transmitting means mounted for movement with respect to the base in either of said two directions and engaging the lever member during movement in one of said directions to move the lever member relatively slowly against the bias of said spring means;

second over-center spring means operatively engaging the base and the contact arm to couple the base and the contact arm for biasing the contact arm in either one of said two directions from a dead-center position of the second over-center spring means and biasing the contact arm in the same direction as the bias of the first over-center spring means when the contact arm is in either one of said two positions to maintain the contact arm in that one position while the lever member is moved from one toward the other of said first and second positions and until the first over-center spring means is moved through its dead-center position by movement of the lever member and the link whereupon the bias of the first over-center spring means is reversed and directed against the bias of the second over-center spring means, the relative magnitudes of the bias forces of the first over-center spring means and the second over-center spring means being such that the bias force of the second over-center spring means is overcome by the bias force of the first over-center spring means, when the forces are directed against one another, to urge the contact arm toward the other of said two positions and the second overcenter spring means through its dead-center position whereupon the bias of the second over-center spring means is reversed so that both the first overcenter spring means and the second over-center spring means will bias the contact arm toward the other of said two positions; and

means connecting the link and the lever member, said means including a pivot and stop means, for allowing limited pivotal movement of the link relative to the lever member such that as the lever member is moved slowly by the motion transmitting means against the bias of said spring means, the link and the lever member will move in fixed relationship with one another and as said first overcenter spring means passes slowly through the dead-center position, the link will pivot rapidly with respect to the lever member in response to the passage of the first over-center spring means through the dead-center position and independent of any movement of the contact arm to allow relatively rapid reversal of the bias of said first over-center spring means and rapid transfer of said contact arm from one to the other of the contact arm positions.

2. The snap-action electric switch of claim 1 including at least two first contacts electrically insulated from one another and at least two second contacts electrically insulated from one another, the second contacts disengaging from the corresponding first contacts essentially simultaneously upon said reversal of the bias force of the first over-center spring means and movement of the contact arm from one toward the other of said two positions.

3. The snap-action switch of claim 1 wherein:

the contact arm is movable between two opposite directions and has two opposite ends;

the lever member has two opposite ends, one of said ends being fixed against movement in either of said opposite directions while the other of said ends is movable in either of said opposite directions between opposite first and second positions;

the first over-center spring means has two opposite ends,

one of which ends pivotally engages one of the ends 10 of the contact arm to bias the contact arm in either of said opposite directions;

the link has two opposite ends, one of which ends pivotally engages the movable end of the lever member and the other of which ends pivotally engages the other end of the first over-center spring means; and

the motion transmitting means is movable in either of said two opposite directions.

4. The snap-action electric switch of claim 3 wherein the lever member is pivotally mounted on the base at said one of the two opposite ends.

5. The snap-action electric switch of claim 3 wherein the second over-center spring means has two opposite ends, one of which ends is fixed against movement in either of said two opposite directions, and the other of which ends pivotally engages the other of the ends of the contact arm to bias the contact arm in either one or said two opposite directions.

6. The snap-action electric switch of claim 5 including at least two first contacts electrically insulated from one another and at least two second contacts electrically insulated from one another, the second contacts breaking contact with the corresponding first contacts essentially simultaneously upon said reversal of the bias force of the first over-center spring means and movement of the contact arm from one toward the other of said two positions.

7. The snap-action electric switch of claim 5 wherein:

the lever member is pivotally mounted on the base at said one of the two opposite ends; and

the second over-center spring means is, pivotally mounted on the base at said one of the two opposite ends. 8. The snap-action electric switch of claim 1 for use with time delay control apparatus having a motion transmitting member capable of movement in either of said two directions wherein:

the base is at least partially of dielectric material; the lever member has two opposite ends; the contact arm is movable between two opposite clirections and has two opposite ends; I

means are provided for pivotally mounting one of said ends of the lever member to the base for rotation of the lever member thereabout in a plane to move the other of said ends in either of said opposite directions between opposite first and second positions;

the first over-center spring means has two opposite ends;

means are provided for pivotally mounting one of the ends of the first over-center spring means to one end of the contact arm to compress the first overcenter spring means and bias the contact arm in either of said opposite directions;

the iink has two opposite ends;

said means connecting the link and the lever member connect one of the ends of the link to the movable end of the lever member;

means are provided for pivotally mounting the other end of the link to the other end of the first overcenter spring means;

the second over-center spring means has two opposite ends;

means are provided for pivotally mounting one end of the second over-center spring means to the base for rotation of the second over-center spring means thereabout in a plane and for pivotally mounting the other end of the second over-center spring means to the other end of the contact arm to compress the second over-center spring means and bias the contact arm in either one of said two opposite directions; and

1 l the motion transmitting means is movable in either of said two opposite directions in response to the movement of said motion transmitting member.

9. The snap-action electric switch of claim 8 including at least two first contacts electrically insulated from one another and at least two second contacts breaking contact with the corresponding first contacts essentially simultaneously upon said reversal of the bias force of the first over-center spring means and movement of the contact arm from one toward the other of said two positions.

10. The snap-action electric switch of claim 8 including further stop means on said base disposed relative to said lever member for precluding movement of the lever member beyond said first and second positions, said further stop means being selectively adjustable to enable accurate 12 location of each of said first and second positions and vary the sensitivity of said switch.

References Cited UNITED STATES PATENTS 2,892,050 6/1959 Fisher 20067 2,770,693 11/1956 Fickel 200-67 2,556,216 6/1951 Raney 200-67 2,936,350 5/1960 Hughey ZOO-67 3,185,786 5/1965 vi'ilson 20067 FOREIGN PATENTS 1,259,429 3/ 1961 France.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, Assistant Examiner. 

1. A SNAP-ACTION ELECTRIC SWITCH CAPABLE OF BEING OPERATED BETWEEN TWO POSITIONS AND NORMALLY URGED TOWARD ONE OF SAID TWO POSITIONS, THE SWITCH COMPRISING: A BASE; AT LEAST ONE FIRST CONTACT FIXED TO THE BASE; A LEVER MEMBER MOUNTED ON THE BASE FOR MOVEMENT IN EITHER OF TWO DIRECTIONS BETWEEN FIRST AND SECOND POSITIONS; A CONTACT ARM; MEANS MOUNTING SAID CONTACT ARM FOR MOVEMENT WITH RESPECT TO SAID BASE IN EITHER OF SAID TWO DIRECTIONS BETWEEN TWO POSITIONS IN RESPONSE TO THE MOVEMENT OF THE LEVER MEMBER BETWEEN THE FIRST AND SECOND POSITIONS; AT LEAST ONE SECOND CONTACT CARRIED BY THE CONTACT ARM FOR ENGAGEMENT WITH THE CORRESPONDING FIRST CONTACT WHEN THE CONTACT ARM IS IN ONE OF SAID TWO POSITIONS AND DISENGAGEMENT FROM THE CORRESPONDING FIRST CONTACT WHEN THE CONTACT ARM IS IN THE OTHER OF SAID TWO POSITIONS; SPRING MANS MOUNTED WITH RESPECT TO THE BASE FOR BIASING THE LEVER MEMBER TOWARD ONE OF SAID FIRST AND SECOND POSITIONS; FIRST OVER-CENTER SPRING MEANS FOR BIASING THE CONTACT ARM IN EITHER OF SAID TWO DIRECTIONS FROM A DEADCENTER POSITION TO THE OVER-CENTER SPRING MEANS LOCATED BETWEEN THE FIRST AND SECOND POSITIONS OF THE LEVER MEMBER; A LINK OPERATIVELY ENGAGING THE OVER-CENTER SPRING MEANS AND THE LEVER MEMBER TO COUPLE THE FIRST OVER-CENTER SPRING MEANS WITH THE LEVER MEMBER SUCH THAT MOVEMENT OF THE LEVER MEMBER FROM ONE OF SAID FIRST AND SECOND POSITIONS TOWARD THE OTHER OF SAID POSITIONS WILL MOVE THE FIRST OVER-CENTER SPRING MEANS THROUGH SAID DEAD-CENTER POSITION AND REVERSE THE BIAS OF THE FIRST OVER-CENTER SPRING MEANS SO AS TO URGE THE CONTACT ARM TOWARD THE OTHER OF SAID FIRST AND SECOND POSITIONS OF THE CONTACT ARM; 